Depth gauge

ABSTRACT

The casing of a diver-held depth gauge comprises a liquid filled chamber in which is carried a pressure indicating mechanism comprising a Bourdon tube, dial and pointer. The chamber extends substantially across the entire casing and is sealed by a rigid plexiglass lens. The lens itself is resiliently mounted in the opening of the casing for limited sliding movement. In addition to the usual function of enabling visual access to the internal indicating mechanism, the lens transmits ambient external pressure to the confined internal liquid.

United States Patent MacNiel [451 Sept. 26, 1972 [54] DEPTH GAUGEInventor:

Assignee:

Filed:

Calif.

References Cited Douglas K. MacNiel, Costa Mesa,

U.S. Divers Co., Santa Ana, Calif. Aug. 11, 1970 Appl. No.: 62,951

US. Cl. ..73/300, 73/41 1, 73/419 Int. Cl ..G0lf 23/20, G011 7/16, G0117/02 Field of Search...92/5 R, 169; 73/411, 419, 323,

UNITED STATES PATENTS Schloss ..73/419 X Alinari. ..73/300 Hopkins..73/43l Pasnak et al ..73/419 X Grandstaff ..73/419 X 3,357,394 12/1967lngham et al. ..73/43l 3,243,496 3/ 1966 Silverstein ..73/431 X3,397,808 8/1968 Jones ..73/323 X Primary Examiner-Louis R. PrinceAssistant ExaminerDaniel M. Yasich Attorney-Gausewitz, Carr & Rothenberg[5 7] ABSTRACT DEPTH GAUGE BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention relates to pressure meters and moreparticularly concerns a diver-held depth gauge of an improvedconstruction that provides maximized protection for internal mechanismsand avoids external exposure of sensitive operating parts.

2. Description of Prior Art Depth gauges, particularly those that arereadily portable and designed to be worn by a diver, generally employ ananeroid mechanism or conventional Bourdon tube with suitable linkage andan indicator calibrated to provide a display of depth in feet or metersas a function of ambient water pressure. A number of devices of thistype provide direct access of the ambient water to the internalmechanism of the gauge. Typical of such devices are the instrumentsdescribed in U.S. Pat. No. 3,187,572 to P. Harland and in US. Pat. No.3,370,470 to G. Neugebauer. Such arrangements are subject to severecorrosion problems. The contaminating effects of contacting sea waterand the particles or debris that may be carried by the water alsodegrade operation. Sea water quickly interferes with and eventuallyprevents operation of the gauge for accurate measurement.

To avoid such problems and to provide protection for delicate pressuresensitive mechanisms, several different arrangements have been suggestedfor sealing the pressure sensitivemechanism within a fluid filledchamber and transmitting ambient external pressure to the confined fluidby means of a flexible diaphragm. Arrangements of this type are shown inthe US. Pats. to R. J. Cerny, No. 2,986,038, T. Stewart, No. 2,935,873,and the US. Pats. to C. Alinari, Nos. 3,121,333 and 3,203,244. In eachof these gauges, a relatively incompressible fluid not only transmitspressure to the sealed pressure sensitive Bourdon tube, but alsoprovides for damping of the motion of moving parts and cushioningagainst shock.

Prior devices, particularly those providing for a wrist-mountedinstrument, include a transparent sealed lens on one side of a casing toprovide visibility of the internal indicating mechanism. On the otherside of the casing, generally on the portion that is adjacent thewearers wrist, there is arranged a flexible diaphragm adapted to respondto ambient water pressure. The diaphragm flexes to transmit pressure tothe confined fluid and thereby to the pressure sensitive mechanismwithin the casing. The requirement of a diaphragm that is suitablyflexible is in direct conflict with other requirements of devices ofthis kind, namely the requirements for ruggedness and the ability towithstand hard wear and rough usage. For this reason, gauges such asthose shown by Stewart, Cemy, and Alinari all must provide additionalrelatively complex and expensive arrangements for protecting thepressure sensitive diaphragm. I

Thus, a rigid guard or screen must be mounted to the casing over thediaphragm and suitable passages or ports formed in or about the guard toadmit ambient water. Not only are these guard devices expensive anddifficult to manufacture, but the relatively restricted ports oropenings therein are themselves subject to becoming clogged or otherwiseinoperative to thereby introduce still further unreliability.

Because a pressure responsive diaphragm operates by flexing throughcomplex curvatures, changing from an initial planar configuration,volume changes within the sealed pressure chamber are not linear withrespect to external pressure changes. Thus, the diaphragm introducesnon-linearity of the reading or requires a compensatory non-linearcalibration of the dial. In either case, errors are present andcompounded as the diaphragm ages and its flexibility changes.

Furthermore, the diaphragm, because of its relatively fragile nature, isgenerally formed with a considerably smaller extent than the extent ofthe entire meter, so that its operative surface area is relativelylimited.

Accordingly, it is an object of the present invention to provide a depthgauge in which the indicating mechanism is entirely mounted in a sealedchamber having an improved arrangement for transmitting pressurethereto.

SUMMARY OF THE INVENTION In carrying out principles of the invention inaccordance with a preferred embodiment thereof, a housing defining achamber has an opening communicating with the chamber and is providedwith a rigid closure member that is resiliently mounted in the openingin sealing relation to the chamber for limited motion in response topressure exerted upon the closure member. A liquid is sealed within thechamber together with means for indicating pressure of the liquid. Anadditional feature of the invention is implemented by making the rigidclosure member of a transparent material such as a relatively thickplexiglass disc that seals the opening and is resiliently mountedtherein for a limited sliding motion by means of a peripheral O-ring.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a pressureresponsive instrument constructed in accordance with principles of thisinvention, and

FIG. 2 is a cross-section of the instrument of FIG. 1.

DETAILED DESCRIPTION As illustrated in FIG. 2, a substantially rigidhousing 10 is formed as a shallow cup or, in effect, as a cylindricalsection having an axial length considerably less than its diameter.Housing 10, which is preferably made of a suitable corrosion resistantmetal such as aluminum or brass, or of a relatively rigid corrosionresistant plastic, has a bottom or fixed end member 12, upstanding sidewalls 11 and beveled corners 13, all integrally formed to thereby definean internal chamber for mounting a pressure sensitive mechanism.

Housing 10 is also provided with integral diametrically opposedextending flanges or lugs 15 that carry bars 17. The latter are spacedfrom the body of the housing to enable a wrist band or strap (not shown)to be secured to the gauge.

Securely mounted to the housing 10 and totally within the chambertherein is an indicating mechanism comprising a Bourdon tube 14. TheBourdon tube 14 is a substantially conventional device and may beevacuated and sealed, or filled with air or other gas under atmosphericpressure and then sealed.

One end of the tube 14 is fixedly attached to a support 16 positionedcentrally of the housing and extending diametrically across the housingfrom one edge thereof to the center. Attached to the free end of theBourdon tube 14 is a conventional linkage and dial operating mechanism(not shown) that is arranged to rotate a pointer 20. The pointer iscarried by a shaft 18 journaled in the fixed support 16.

Rigidly affixed to the support 16 is a dial face 22 hearing suitableindicia that enable visual readout of the angular position of thepointer 20.

Dial 22 has the edges thereof inserted in a resilient circumferentialtube 19. The latter is formed with a continuous slot'that resilientlyreceives and frictionally engages the edge of the dial. To allow liquidcommunication across the dial, tube 19 extends less than a full360'Hround the dial.

Side wall 11 of the housing is formed with an annular groove 21 thatreceives and securely retains the resilient tube 19 together with thedial 22. By this means, the entire pressure sensitive, indicatingassembly is mounted to and carried by the housing.

To facilitate assembly, the inner diameter of housing below groove 21 ismade substantially equal to the diameter of dial 22 whereby the latter(with tube thereon) may not be inadvertently positioned below thegroove. In effect, a shoulder is provided upon which the dial tube 19 isseated. The inner diameter 23 of the housing above the groove isslightly larger to allow insertion of the dial and tube.

The opening of the housing is substantially filled and closed by a rigidclosure member 24. Closure member 24 is a relatively thick plate oftransparent material such as glass or transparent plastic and has arelatively shallow peripheral annular groove 26 formed in its edge. Arelatively deeper mating groove 28 is formed in the larger diameterportion 23 of the wall of the cylindrical housing section adjacent thechamber opening. A resilient O-ring 30, formed of elastomeric material,is captured within and confined by the mating grooves 26, 28, to therebyresiliently secure and seal the closure member 24 to the housing 10within the opening thereof. The edge of member 24 is a close but freesliding fit upon the surface of the larger diameter portion 23 as willbe described below. To afford some magnification the closure member maybe made slightly convex.

A substantially incompressible liquid 32, such as ethylene glycol or anequivalent viscous and incompressible oil, completely fills the chamberwithin the housing 10 and is sealed therein by the lens or closuremember 24. Liquid 32 protects the sensitive pressure responsivemechanism from corrosive effects of the salt water or other ambientenvironment and achieves a uniform application of pressure to the entireexterior surface of the Bourdon tube 14. As is well known, a viscousliquid such as oil, provides a damping of vibration induced motion andalso protects sensitive parts from external shock.

Housing 10 is provided with an aperture 34 in which is threadedlyengaged a removable cap or plug 36 that is sealed to the housing.

For optimum operation of the described gauge, the chamber is completelyfilled with the confined liquid and all bubbles of air or gas areeliminated. For this reason, the plug 36 is provided to enable carefulfilling of the previously assembled structure including pressuresensitive mechanism and chamber sealing closure member 24. Havingcarefully filled the chamber so as to prevent formation or entrapment ofbubbles of air or gas, the plug 36 may then be inserted within theaperture 34 and sealed and secured therein. Thus, assembly of theinstrument may be completed without any disturbance which may introducebubbles into the interior of the housing 10.

If deemed necessary or desirable to further insure a bubble-free liquidwithin the casing, the entire assembly except for the wrist strap isassembled while immersed in a body of the same liquid. The dial 22 andtube 19 (together with the Bourdon tube mechanism carried thereby) arefirst positioned to cause the tube 19 to be resiliently secured ingroove 21. O-ring 30 is located in groove 28, the housing is inverted,and lens closure member 24 is then pressed into place whereby the O-ring30 is forced into groove 26 of the lens. During the latter step, liquidwithin the housing is displaced through aperture 34 to provide ableeding operation that ensures removal of entrapped gas.

The plug 36 may be removed if necessary for refilling of the chamber asmay be required upon repair or replacement of various parts of thegauge.

It will be seen that the closure member 24 provides a pressuretransmitting member having an externally wetted surface, namely asurface in contact with the ambient water, of maximized dimension withrespect to the overall size of the instrument. This closure memberperforms several different functions when arranged and constructed asdescribed above. Acting as a transparent lens, it provides visual accessto the dial scale and pointer. Being slidably mounted for limitedmotion, without flexure, toward and away from the chamber confining theincompressible fluid 32 and pressure sensitive mechanism, the closuremember acts as a pressure transmitting member. it thus additionallyperforms the usual function of the flexible diaphragms employed in priordevices. Further, having a substantial thickness and being rigid andrugged, the closure member protects the sensitive mechanism within thehousing.

Sealing O-ring 30 also performs several functions in the describedarrangement. First, as is common for such a device, it provides apressure and liquid seal for the housing chamber, confining the liquid32 therein and preventing leakage. Concomitantly, the O-ring 30 providesa resilient mounting for the rigid closure member 24 that enables alimited sliding motion thereof to and from the housing chamber inaccordance with ambient pressure variations.

Considering the relatively shallow depth of the cylindrical housing 10as compared with its large diameter, it will be readily seen that only asmall displacement of the closure member 24 axially of the cylindricalhousing 10, will achieve a relatively large change in the volume of thesealed chamber within the housing. The sliding motion of the lens isprovided by a limited torsional or rolling deformation of the O-ring 30.Any such volume change within the housing acts directly upon the elasticBourdon tube.

As mentioned above, the flexing action of the conventional diaphragm maybe a source of unacceptable errors in a precision measuring instrument.The described closure member, on the other hand,

completely avoids this type of error. Member 24 is sufficiently thickand rigid to avoid any flexing. Thus, it slides as a unit through alimited distance. This arrangement provides volume changes within thechamber that are directly proportional to external pressure changesthrough the range of motion of closure member. Even the relativelylimited slidable axial motion of lens 24 that is afforded by theresilient O-ring mounting thereof will provide a relatively large rangeof pressure readings. For example, lens 24 travels but 0.017 inch, ingoing from depths of to 300 feet, in order to provide a full scaletravel of pointer 20 of a common Bourdon tube pressure sensitivemechanism. Thus, the overall dimensions of the gauge assembly may beoptimized. The gauge may have a relatively large diameter and arelatively small axial extent for convenient attachment to a wrist.

It will be seen that the described oil-filled depth gauge provides animproved and simplified arrangement that affords significant economiesin manufacture and yet entails no compromise in accuracy or operation.No special screens, guards, or apertures therefor need be designed orbuilt. The sealing O-ring commonly employed for the lens concomitantlyprovides a resilient mounting for the lens so that the usual flexiblediaphragm of prior devices is wholly eliminated without loss of itsfunction. Not only is the previous function of the prior art diaphragmretained, but such function is actually enhanced by the describedarrangement which enables use of a pressure transmitting member, lens24, of increased linearity, and of maximized size and ruggedness needingno further protection.

The foregoing detailed description is to be clearly understood as givenby way of illustration and example only, the spirit and scope of thisinvention being limited solely by the appended claims.

What is claimed is:

l. A pressure responsive instrument, comprising:

a rigid housing defining a chamber,

said housing having an opening therein communicating with said chamber,

a rigid transparent pressure responsive closure member mounted in saidopening for limited movement toward and away from said chamber,

a liquid in said chamber and substantially filling the same,

means for sealing said closure member in said opening throughout itslimited range of movement, to seal said liquid within said chamber, and

means disposed in said chamber for indicating pressure of said liquid,whereby pressure exerted upon said closure member is transmitted to saidliquid and visibly indicated by said indicating means through said rigidtransparent pressure responsive closure member.

2. The instrument of claim 1 wherein said sealing means includes meansfor mounting said closure member to said housing for limited slidingmotion toward and away from said chamber.

3. A depth gauge, comprising:

a housing defining a chamber,

said housing having an opening therein communicating with said chamber,

a rigid closure member resiliently mounted in said opening in sealingrelation to said housing for limited motion toward and away from saidchamber in response to pressure exerted upon said 5. The gauge of claim3 wherein said chamber is generally cylindrical and has an axial lengthless than its diameter, wherein a fixed end member is sealed to saidhousing at one end of said chamber, and wherein said opening issubstantially co-extensive with the other end of said chamber.

6. The gauge of claim 5 wherein said housing has an annular groove atsaid other end of said chamber, wherein said closure member has anannular groove in a peripheral edge thereof, and wherein said closuremember is mounted in said opening by means of an O- ring confined withinboth said grooves, whereby said O- ring is deformed within said groovesas said closure member slides axially of said cylindrical section.

7. The gauge of claim 6 wherein said housing includes an aperturetherein for communication with said chamber, and

a plug removably sealed in said aperture.

8. The depth gauge of claim 3 wherein said closure member is mounted forlimited sliding motion toward and away from said chamber.

9. A pressure responsive instrument comprising:

a rigid housing defining a chamber,

said housing having an opening therein communicating with said chamber,

a rigid pressure responsive closure member formed of a transparent platesubstantially completely filling said opening, said transparent platebeing mounted in said opening for limited movement toward and away fromsaid chamber,

a liquid in said chamber and substantially filling the same,

means for sealing said transparent plate in said opening to seal saidliquid within said chamber, said sealing means comprising:

a flexible element interposed in sealing relationship between theperiphery of said plate and the portion of said housing encompassingsaid opening, and

means disposed in said chamber for indicating pres sure of said liquid,whereby pressure exerted upon said transparent plate is transmittedthereby to said liquid and visibly indicated by said indicating meansthrough said transparent plate.

10. A pressure responsive instrument, comprising:

a rigid housing defining a chamber,

said housing having an opening therein communicating with said chamber,

a rigid closure member mounted in said opening for limited movementtoward and away from said chamber, said closure member being atransparent plate substantially completely filling said opening,

a liquid in said chamber,

means for sealing said closure member in said opening to seal saidliquid within said chamber, said sealing means comprising: an O-ringinterposed in sealing relationship between the periphery of said plateand the portion of said housing encompassing said opening, the peripheryof said plate and said encompassing portion of said housing being formedwith mating grooves, said O-ring being mounted in sealing relation inboth said grooves, and means for indicating the pressure of said liquid,

whereby pressure exerted upon said said closure member is transmitted tosaid liquid and indicated by said indicating means, said indicatingmeans being visible through said transparent plate.

l l. The instrument of claim 10 wherein said housing is formed with athird groove positioned inwardly of said opening relative to saidclosure member, and wherein said means for indicating pressure comprisesa dial, and

a slotted tube resiliently retained in said third groove, said dialhaving a peripheral edge portion mounted within the slot of said tube.

12. A depth gauge, comprising:

a housing defining a chamber,

said housing having an opening therein communicating with said chamber,

a rigid closure member resiliently mounted in said opening in sealingrelation to said housing for limited motion toward and away from saidchamber in response to pressure exerted upon said closure member, saidclosure member being transparent,

a liquid sealed within said chamber, and

indicating means disposed within said chamber for indicating thepressure of said liquid, said indicating means being visible throughsaid closure member,

said indicating means comprising:

a Bourdon tube mounted in said chamber,

a dial disposed between said Bourdon tube and said closure member andhaving a diameter substantially equal to the diameter of said chamber,and

a pointer operatively connected with the Bourdon tube for movement oversaid dial,

said housing being formed with an annular groove, and a slotted tubesubstantially circumscribing and retaining a peripheral edge portion ofsaid dial in the slot thereof, said slotted tube being resilientlyconfined within said groove.

13. A depth gauge, comprising:

a housing defining a chamber,

said housing having an opening therein communicating with andsubstantially coextensive with one end of said chamber,

said housing being generally cylindrical and having an axial length lessthan its diameter,

a fixed end member sealed to said housing at the other end of saidchamber,

a rigid transparent pressure responsive closure member resilientlymounted in said opening in sealing relation to said housing for alimited motion toward and away from said chamber in 'iesponse topressure exerted upon said closure member,

a liquid sealed within and filling said chamber and in full contact withsaid rigid transparent closure member, and

indicating means disposed within said chamber and visible through saidrigid transparent pressure responsive closure member for indicatingpressure of said liquid.

14. An underwater depth gauge comprising:

a rigid housing defining a chamber,

said housing having an opening therein communicating with said chamber,

a rigid transparent pressure responsive closure member mounted in saidopening for limited movement toward and away from said chamber,

a liquid in said chamber,

means for securing and sealing said closure member to and within saidopening to seal said liquid within said chamber, to retain said closuremember in a predetermined position when it is subjected to substantiallyatmospheric pressure, and to permit limited movement thereof when it issubjected to the greater pressure of a body of water in which the gaugeis submerged, said securing and sealing means comprising meanscircumscribing the periphery of said closure member and securedthroughout its extent in sealing relation both to said closure memberand to the opening of said chamber, and

means within said chamber and visible through said rigid transparentclosure member for indicating pressure of said liquid, whereby pressureexerted upon said closure member is transmitted to said liquid andvisibly displayed by said indicating means through said transparentpressure responsive closure member.

15. The instrument of claim 14 wherein said opening and the edge of saidclosure member are formed with mutually facing and mating peripheralgrooves, and wherein said circumscribing means comprises an elastictoroid captured within both of said mating grooves.

16. A depth gauge comprising:

a housing formed as a shallow cup open at one end substantially acrossits entire extent,

pressure indicating means mounted within the hous-.

ing, and visible through said open end,

a liquid within and substantially filling said housing and completelyimmersing said indicating means therein,

a rigid transparent pressure responsive closure member substantiallyfilling the open end of said housing and having its inner surface incontact with said liquid,

said rigid transparent closure member being mounted to said housing forlimited sliding motion toward and away from the interior of the housingso as to transmit external pressure to said liquid over substantiallythe entire extent of the housing open end, and

means for sealing said rigid transparent pressure responsive closuremember to and within the open end of said housing so as to seal saidliquid and indicating means within said housing.

17. The depth gauge of claim 16 wherein said sealing means comprises aset of mating grooves in said housing and in the peripheral edge of saidrigid transparent pressure responsive closure member, and an elastomericsealing element captured within and confined by the mating grooves.

18. A depth gauge for strapping on the wrist of a skin diver, whichcomprises:

a shallow, cup-shaped, substantially rigid housing which is open at theupper end thereof,

a dial provided in generally parallel relationship to said open upperend of said housing,

an indicator mounted within said housing and movable to differentpositions relative to said dial, at least part of said indicator beingvisible through said open upper end of said housing,

a Bourdon tube mounted within said housing and operatively connectedwith said indicator, whereby the pressure sensed by said Bourdon tubewill effect a corresponding positioning of said indicator relative tosaid dial, a substantially incompressible liquid substantiallycompletely filling said housing and immersing said Bourdon tube and saidindicator, a substantially rigid member disposed at the open upper endof said housing to confine said liquid therein, the periphery of saidmember being adjacent said open upper end of said housing,

at least parts of said member being transparent whereby to permit thediver to look through said member and see said indicator, and resilientsealing and motion-permitting means provided between the periphery ofsaid member and said open upper end of said housing, said last-namedmeans effecting sealing of said member relative to said housing wherebyto prevent either ingress of sea water into said housing or egress ofsaid liquid from said houssaid last-named means permitting a smalldegree of movement of said member toward the bottom of said housing inresponse to a descent by the diver into the sea,

said small degree of movement effecting an increase in the pressure ofsaid liquid within said housing to thus cause said Bourdon tube to movesaid indicator relative to said dial. 19. A depth gauge comprising: ahousing defining a chamber,

said housing having an opening therein communicating with andsubstantially co-extensive with one end of said chamber,

said housing being generally cylindrical and having an axial length lessthan its diameter,

a fixed end member sealed to said housing at the other end of saidchamber,

a rigid pressure responsive closure member mounted in said opening insealing relation to said housing for limited motion toward and away fromsaid chamber in response to pressure exerted upon said closure member,

first and second mating grooves formed respectively in the periphery ofsaid closure member and in the portion of said housing that encompassessaid opening,

an O-ring captured in both said grooves and interposed in sealingrelation between the periphery of said closure member and the portion ofsaid housing that encompasses said opening,

a liquid sealed within said chamber, and

indicating means disposed within said chamber for indicating pressure ofsaid liquid,

said rigid pressure responsive closure member being transparent wherebysaid indicating means is visible through said transparent closuremember.

20. A depth gauge for a skin diver comprising:

a rigid housing having a side wall and first and second ends, saidhousing defining a chamber that extends substantially throughout theentire housing, said housing having an opening therein extendingsubstantially across one end of said chamber,

a fixed end member sealed to said housing at the other end of saidchamber,

indicator .means mounted within said chamber and movable to differentpositions to provide a visual display of pressure,

a Bourdon tube mounted within said chamber and operatively connectedwith said indicator means, whereby pressure exerted upon said Bourdontube will effect a corresponding display of said indicator means,

a substantially incompressible liquid substantially completely fillingsaid chamber and immersing said Bourdon tube and said indicator means,

a rigid pressure responsive closure member positioned in said openingfor limited movement toward and away from said chamber, said rigidclosure member having its inner face in substantially full contact withsaid liquid,

at least part of one of said members being transparent whereby to permitthe diver to look through said one member and see said indicator means,

means for mounting said rigid closure member to said housing for saidlimited motion, and for resiliently securing and sealing said rigidclosure member to and within said opening to resiliently retain saidclosure member in position and to seal said liquid within said chamber,said mounting, securing and sealing means comprising a resilient elementcontinuously interconnected to and between the periphery of said rigidclosure member and the surrounding portion of said chamber within saidopening, said resilient element being secured throughout its extent insealing relation to said rigid closure member and to the opening of saidchamber, whereby an increase in pressure exerted upon said closuremember is transmitted to said liquid over substantially all of saidclosure member face by limited motion of said closure member toward saidchamber, to thereby compress said Bourdon tube and move said indicatormeans to provide a display of pressure visible through said onetransparent member part, and whereby said closure member is returned toan initial position when said increase in pressure is no longer exertedupon said closure member.

1. A pressure responsive instrument, comprising: a rigid housingdefining a chamber, said housing having an opening therein communicatingwith said chamber, a rigid transparent pressure responsive closuremember mounted in said opening for limited movement toward and away fromsaid chamber, a liquid in said chamber and substantially filling thesame, means for sealing said closure member in said opening throughoutits limited range of movement, to seal said liquid within said chamber,and means disposed in said chamber for indicating pressure of saidliquid, whereby pressure exerted upon said closure member is transmittedto said liquid and visibly indicated by said indicating means throughsaid rigid transparent pressure responsive closure member.
 2. Theinstrument of claim 1 wherein said sealing means includes means formounting said closure member to said housing for limited sliding motiontoward and away from said chamber.
 3. A depth gauge, comprising: ahousing defining a chamber, said housing having an opening thereincommunicating with said chamber, a rigid closure member resilientlymounted in said opening in sealing relation to said housing for limitedmotion toward and away from said chamber in response to pressure exertedupon said closure member, said closure member being transparent, aliquid sealed within said chamber, and indicating means disposed withinsaid chamber for indicating the pressure of said liquid, said indicatingmeans being visible through said closure member.
 4. The gauge of claim 3wherein said indicating means comprises a Bourdon tube mounted in saidchamber, a dial disposed between said Bourdon tube and said closuremember and having a diameter substantially equal to the diameter of saidchamber, and a pointer operatively connected with the Bourdon tube formovement over said dial.
 5. The gauge of claim 3 wherein said chamber isgenerally cylindrical and has an axial length less than its diameter,wherein a fixed end member is sealed to said housing at one end of saidchamber, and wherein said opening is substantially co-extensive with theother end of said chamber.
 6. The gauge of claim 5 wherein said housinghas an annular groove at said other end of said chamber, wherein saidclosure member has an annular groove in a peripheral edge thereof, andwherein said closure member is mounted in said opening by means of anO-ring confined within both said grooves, whereby said O-ring isdeformed within said grooves as said closure member slides axially ofsaid cylindrical section.
 7. The gauge of claim 6 wherein said housingincludes an aperture therein for communication with said chamber, and aplug removably sealed in said aperture.
 8. The depth gauge of claim 3wherein said closure member is mounted for limited sliding motion towardand away from said chamber.
 9. A pressure responsive instrumentcomprising: a rigid housing defining a chamber, said housing having anopening therein communicating with said chamber, a rigid pressureresponsive closure member formed of a transparent plate substantiallycompletely filling said opening, said transparent plate being mounted insaid opening for limited movement toward and away from said chamber, aliquid in said chamber and substantially filling the same, means forsealing said transparent plate in said opening to seal said liquidwithin said chamber, said sealing means comprising: a flexible elementinterposed in sealing rElationship between the periphery of said plateand the portion of said housing encompassing said opening, and meansdisposed in said chamber for indicating pressure of said liquid, wherebypressure exerted upon said transparent plate is transmitted thereby tosaid liquid and visibly indicated by said indicating means through saidtransparent plate.
 10. A pressure responsive instrument, comprising: arigid housing defining a chamber, said housing having an opening thereincommunicating with said chamber, a rigid closure member mounted in saidopening for limited movement toward and away from said chamber, saidclosure member being a transparent plate substantially completelyfilling said opening, a liquid in said chamber, means for sealing saidclosure member in said opening to seal said liquid within said chamber,said sealing means comprising: an O-ring interposed in sealingrelationship between the periphery of said plate and the portion of saidhousing encompassing said opening, the periphery of said plate and saidencompassing portion of said housing being formed with mating grooves,said O-ring being mounted in sealing relation in both said grooves, andmeans for indicating the pressure of said liquid, whereby pressureexerted upon said said closure member is transmitted to said liquid andindicated by said indicating means, said indicating means being visiblethrough said transparent plate.
 11. The instrument of claim 10 whereinsaid housing is formed with a third groove positioned inwardly of saidopening relative to said closure member, and wherein said means forindicating pressure comprises a dial, and a slotted tube resilientlyretained in said third groove, said dial having a peripheral edgeportion mounted within the slot of said tube.
 12. A depth gauge,comprising: a housing defining a chamber, said housing having an openingtherein communicating with said chamber, a rigid closure memberresiliently mounted in said opening in sealing relation to said housingfor limited motion toward and away from said chamber in response topressure exerted upon said closure member, said closure member beingtransparent, a liquid sealed within said chamber, and indicating meansdisposed within said chamber for indicating the pressure of said liquid,said indicating means being visible through said closure member, saidindicating means comprising: a Bourdon tube mounted in said chamber, adial disposed between said Bourdon tube and said closure member andhaving a diameter substantially equal to the diameter of said chamber,and a pointer operatively connected with the Bourdon tube for movementover said dial, said housing being formed with an annular groove, and aslotted tube substantially circumscribing and retaining a peripheraledge portion of said dial in the slot thereof, said slotted tube beingresiliently confined within said groove.
 13. A depth gauge, comprising:a housing defining a chamber, said housing having an opening thereincommunicating with and substantially coextensive with one end of saidchamber, said housing being generally cylindrical and having an axiallength less than its diameter, a fixed end member sealed to said housingat the other end of said chamber, a rigid transparent pressureresponsive closure member resiliently mounted in said opening in sealingrelation to said housing for a limited motion toward and away from saidchamber in response to pressure exerted upon said closure member, aliquid sealed within and filling said chamber and in full contact withsaid rigid transparent closure member, and indicating means disposedwithin said chamber and visible through said rigid transparent pressureresponsive closure member for indicating pressure of said liquid.
 14. Anunderwater depth gauge comprising: a rigid housing defining a chamber,said housing havIng an opening therein communicating with said chamber,a rigid transparent pressure responsive closure member mounted in saidopening for limited movement toward and away from said chamber, a liquidin said chamber, means for securing and sealing said closure member toand within said opening to seal said liquid within said chamber, toretain said closure member in a predetermined position when it issubjected to substantially atmospheric pressure, and to permit limitedmovement thereof when it is subjected to the greater pressure of a bodyof water in which the gauge is submerged, said securing and sealingmeans comprising means circumscribing the periphery of said closuremember and secured throughout its extent in sealing relation both tosaid closure member and to the opening of said chamber, and means withinsaid chamber and visible through said rigid transparent closure memberfor indicating pressure of said liquid, whereby pressure exerted uponsaid closure member is transmitted to said liquid and visibly displayedby said indicating means through said transparent pressure responsiveclosure member.
 15. The instrument of claim 14 wherein said opening andthe edge of said closure member are formed with mutually facing andmating peripheral grooves, and wherein said circumscribing meanscomprises an elastic toroid captured within both of said mating grooves.16. A depth gauge comprising: a housing formed as a shallow cup open atone end substantially across its entire extent, pressure indicatingmeans mounted within the housing, and visible through said open end, aliquid within and substantially filling said housing and completelyimmersing said indicating means therein, a rigid transparent pressureresponsive closure member substantially filling the open end of saidhousing and having its inner surface in contact with said liquid, saidrigid transparent closure member being mounted to said housing forlimited sliding motion toward and away from the interior of the housingso as to transmit external pressure to said liquid over substantiallythe entire extent of the housing open end, and means for sealing saidrigid transparent pressure responsive closure member to and within theopen end of said housing so as to seal said liquid and indicating meanswithin said housing.
 17. The depth gauge of claim 16 wherein saidsealing means comprises a set of mating grooves in said housing and inthe peripheral edge of said rigid transparent pressure responsiveclosure member, and an elastomeric sealing element captured within andconfined by the mating grooves.
 18. A depth gauge for strapping on thewrist of a skin diver, which comprises: a shallow, cup-shaped,substantially rigid housing which is open at the upper end thereof, adial provided in generally parallel relationship to said open upper endof said housing, an indicator mounted within said housing and movable todifferent positions relative to said dial, at least part of saidindicator being visible through said open upper end of said housing, aBourdon tube mounted within said housing and operatively connected withsaid indicator, whereby the pressure sensed by said Bourdon tube willeffect a corresponding positioning of said indicator relative to saiddial, a substantially incompressible liquid substantially completelyfilling said housing and immersing said Bourdon tube and said indicator,a substantially rigid member disposed at the open upper end of saidhousing to confine said liquid therein, the periphery of said memberbeing adjacent said open upper end of said housing, at least parts ofsaid member being transparent whereby to permit the diver to lookthrough said member and see said indicator, and resilient sealing andmotion-permitting means provided between the periphery of said memberand said open upper end of said housing, said last-named means effectingsealing of saiD member relative to said housing whereby to preventeither ingress of sea water into said housing or egress of said liquidfrom said housing, said last-named means permitting a small degree ofmovement of said member toward the bottom of said housing in response toa descent by the diver into the sea, said small degree of movementeffecting an increase in the pressure of said liquid within said housingto thus cause said Bourdon tube to move said indicator relative to saiddial.
 19. A depth gauge comprising: a housing defining a chamber, saidhousing having an opening therein communicating with and substantiallyco-extensive with one end of said chamber, said housing being generallycylindrical and having an axial length less than its diameter, a fixedend member sealed to said housing at the other end of said chamber, arigid pressure responsive closure member mounted in said opening insealing relation to said housing for limited motion toward and away fromsaid chamber in response to pressure exerted upon said closure member,first and second mating grooves formed respectively in the periphery ofsaid closure member and in the portion of said housing that encompassessaid opening, an O-ring captured in both said grooves and interposed insealing relation between the periphery of said closure member and theportion of said housing that encompasses said opening, a liquid sealedwithin said chamber, and indicating means disposed within said chamberfor indicating pressure of said liquid, said rigid pressure responsiveclosure member being transparent whereby said indicating means isvisible through said transparent closure member.
 20. A depth gauge for askin diver comprising: a rigid housing having a side wall and first andsecond ends, said housing defining a chamber that extends substantiallythroughout the entire housing, said housing having an opening thereinextending substantially across one end of said chamber, a fixed endmember sealed to said housing at the other end of said chamber,indicator means mounted within said chamber and movable to differentpositions to provide a visual display of pressure, a Bourdon tubemounted within said chamber and operatively connected with saidindicator means, whereby pressure exerted upon said Bourdon tube willeffect a corresponding display of said indicator means, a substantiallyincompressible liquid substantially completely filling said chamber andimmersing said Bourdon tube and said indicator means, a rigid pressureresponsive closure member positioned in said opening for limitedmovement toward and away from said chamber, said rigid closure memberhaving its inner face in substantially full contact with said liquid, atleast part of one of said members being transparent whereby to permitthe diver to look through said one member and see said indicator means,means for mounting said rigid closure member to said housing for saidlimited motion, and for resiliently securing and sealing said rigidclosure member to and within said opening to resiliently retain saidclosure member in position and to seal said liquid within said chamber,said mounting, securing and sealing means comprising a resilient elementcontinuously interconnected to and between the periphery of said rigidclosure member and the surrounding portion of said chamber within saidopening, said resilient element being secured throughout its extent insealing relation to said rigid closure member and to the opening of saidchamber, whereby an increase in pressure exerted upon said closuremember is transmitted to said liquid over substantially all of saidclosure member face by limited motion of said closure member toward saidchamber, to thereby compress said Bourdon tube and move said indicatormeans to provide a display of pressure visible through said onetransparent member part, and whereby said closure member is returned toan iNitial position when said increase in pressure is no longer exertedupon said closure member.